This invention relates to a method and apparatus to control tensioning by a winch disposed toward the lower drift of an inclined mine seam and coupled by a tension means to a cable trolley adapted to move along the face of a mine seam to guide and loop a trailing cable and/or water hose extending onto the mining machine. More particularly, the present invention relates to such a method and apparatus wherein the winch is controlled in response to a signal that varies with the distance between the cable trolley and the mining machine or a signal which varies with the pull by the trailing cable and/or water hose upon the mining machine and using the signal for controlling the winch to exert tension inversely proportional to the distance between the cable trolley and the mining machine.
In U.S. Pat. No. 4,103,974, assigned to the Assignee of this invention, there is disclosed a cable carriage and spillplate housing assembly for a mining machine wherein the spillplate housing protectively encloses the cable carriage which includes a pulley to form a reverse bend in a cable. The cable extends along an internal duct in the housing and one end of the cable is connected to the mining machine. A tension reel includes a rope coupled to the cable carriage for advancing the carriage within the spillplate housing. The tension reel is supported at the end of the spillplate housing which is opposite from the end where the cable emerges from the housing. The cable includes an electrical power cable and hose which are separately carried by grooves in one or more pulleys. The cable carriage loops, guides and tensions the trailing cable by connection of the cable carriage to the tension reel forming a winch. The spillplate housing has a slot along the length thereof. The slot is normally closed by rubber strips to permit passage of the cable to the mining machine while moving along the course of travel at the mine face.
When the cable carriage or trolley is used to loop, guide and tension a drum-cutting mining machine disposed in an inclined mine seam, the tension or pull imposed on the trailing cable varies with the position of the cable trolley. The pull on the cable is produced by the tension exerted by the winch. The tension is transmitted by way of the cable trolley to the two portions of the looped and guided trailing cable. A pull is also imposed on the cable due to the downward force resulting from the weight of the trailing cable. This downward force varies with the slope of the seam and the length of the trailing cable portion extending from the cable inlet on the coal-cutting mining machine to the cable trolley. The downward force on the cable reaches a maximum when the mining machine is at the upper end of its travel where the cable trolley is located at the greatest distance from the mining machine; whereas the downward force on the cable is at a minimum when the cable trolley is at a point in travel closest to the mining machine which occurs at the lower end of the machine travel. The total force on the cable at the inlet on the mining machine is the sum of the downward force imposed on the cable and that portion of the tension imposed by the winch or tension reel upon the trailing portion of the cable. Consequently, when the mining machine moves, the pull by the trailing cable imposed on the cable inlet on the mining machine also varies continuously with the position of the cable trolley. The tension stress on the cable considerably affects its service life and, consequently, it is desirable to reduce the maximum value of the pull or tension on the cable and particularly fluctuations to the pull or tension.